This application claims priority to United Kingdom Patent Application No. 0004715.9 filed Feb. 28, 2000 and United Kingdom Patent Application No. 0019201.3 filed Aug. 7, 2000.
This invention relates to a method and apparatus for adjusting automotive seat mechanisms and other mechanisms.
Mechanical seat adjustment mechanisms are the subject of a very large number of published patent specifications. Examples of prior seat adjustment mechanism are shown in GB 2,311,094 and GB 2,073,094, although it will be appreciated that there are a large number of other types of seat adjustment mechanisms. There is an endless quest for improvements in such mechanisms in terms of improvements in efficacy and cost effectiveness. The present invention seeks to provide improvements in relation to at least one of these areas.
More specifically, mechanisms for the stepless adjustment of automotive seat backs relative to automotive seat bases are well known. One of the main problem areas in terms of efficacy and cost-effectiveness relates to the fact that such mechanisms need to provide stepless adjustment in combination with the ability to withstand enormous forces arising from automotive impacts leading to seat-belt-transmitted forces having a very large turning moment at the seat pivot. An additional problem relates to backlash which can develop within the seat adjustment mechanisms and in particular in gear type seat adjustment mechanisms. Such backlash results from clearances between the mating mechanical elements which may be required for operation, arise due to inaccuracies in manufacture, or develop due to wear. Backlash within a seat adjustment mechanism is however undesirable in terms of passenger comfort, safety, and also can increase wear on the seat mechanism components.
The present invention seeks to provide a new design approach to the construction of steplessly adjustable seat (and other) mechanisms, in accordance with the following.
According to the invention there is provided method and apparatus for adjusting automotive seat and other mechanisms as defined in the accompanying claims.
In an embodiment of the invention described below there is provided a method and apparatus in which locking of a pivot mechanism is used, for example, in an automotive seat pivot or related adjustable seat mechanism, and is achieved by the use of a magneto-rheological (MR) or electro-rheological (ER) fluid in association with a displacement-sensitive mechanism whereby the combination is responsive to selective changes in the status of the fluid in accordance with the principle that when the fluid is selectively caused to adopt its rheologically activated status it interacts with the mechanism on account of the volume-sensitive pumping action (as it may be termed) of the latter whereby the mechanism is effectively locked when filled (or sufficiently filled) with such a fluid.
By providing the combination of a selectively rheologically status-changeable fluid in association with a volume-sensitive mechanism (for example having a pumping action), the means is provided for achieving a selective and stepless locking action which is instantly (or at least quickly) changeable from its locking to its unlocking status by mere actuation of a magneto or electro-responsive system and without the need for the conventional mechanical disengagement of pawls from ratchets or friction elements from friction surfaces to which they are locked.
Moreover, the use of MR/ER fluids enables the adoption of mechanisms having only modest levels of manufacturing tolerances (and thus which can be manufactured at correspondingly relatively modest costs), and this is due to the fact that the MR/ER fluids interact with the mechanism in a second and likewise unexpected manner in the sense that the adoption of modest and cost-effective tolerances is offset by the ability of the MR/ER fluids (in their activated condition) to interact with the interstices of the associated mechanism (but only in the volume-sensitive and/or pumping environment) so as to offset what might otherwise be arguably unacceptably low manufacturing standards. The MR/ER fluids also effectively off set and reduce any backlash within the mechanisms do to clearances developing as a result of tolerance variations. In addition as the mechanism wears the tolerance variations increase. The MR/ER fluids are able to compensate for this increase, maintaining the overall standard of the mechanism, and maintaining a secure mechanism with little backlash
Accordingly, it can be seen that the embodiments of the invention offer a system in which a fluid medium having selectively controllable properties which enable those properties to be conveniently and instantly switched from one status to another, is able to perform a function which is, in principle, not within the previously realised operational parameters of such fluids. The present invention""s embodiments take no account of previous unpublished proposals for the use of such fluids in damping mechanisms, useful though such functions may be. Conventional damping fluids have no function whatever in relation to the locking of mechanisms, and are likewise of no utility for the purposes of the present invention. The embodiments of the present invention take advantage of the known property of the changeable status of magneto- and electro-rheological fluids, and use this known property in association with a mechanism which is sensitive to (and thus responds differently according to) the changes in those rheological properties which can be selectively commanded by the operator.
As to the mechanisms which, in association with MR and ER fluids can provide the necessary responsiveness to that status change, the following applies. One embodiment of the invention which employs such a mechanism utilises the fluid volume implications inherent in (but previously unappreciated) the meshing relationship between a toothed annular internal periphery gear and a pinion meshing therewith and having a numerical tooth differential as between the two gears whereby the known effect of such a twin gear train is utilised in present seat adjustment mechanisms (for stepless control of the seat back angular position). Such a mechanism requires a high degree of precision manufacture. The tolerances required are fine in order to achieve the necessary absence of backlash in the mechanism when in use.
The present invention in one of its embodiments, uses the previously unrecognised fluid volume implications of this gear train in combination with the status-change selectively available properties of MR and ER fluids to enable such a mechanism to be effective in use without the need for the high degree of precision which has hitherto have been required.
Other related mechanisms exist which can be likewise locked in similar way. Such mechanisms share with the above-mentioned embodiment the following properties including (as previously discussed) volume sensitivity.
Said volume-sensitive mechanism comprise in the embodiments a positive displacement mechanism. Examples of such mechanisms including gear lobe mechanisms, piston mechanisms, and peristaltic mechanisms.
In the embodiments the effect of the positive displacement characteristic of the mechanism is to cause the actual displacement of a specific volume of fluid, such displacement involving, effectively, a fluid coupling from the positive displacement device to, in the embodiments, a fluid flow restriction device whereby the effect of the controllable flow characteristic of the MR or ER fluid effectively interposes a medium allowing (or not) the actual displacement of such fluid by the relative movement of the parts of the positive displacement device driving same.
In the embodiments the positive displaced fluid is able, when the MR/ER fluid has not been caused to adopt its activated non-free flowing condition, to circulate within the mechanism from the zone of displacement to a flow-and-return zone which permits those functions namely displacement, outward flow and return. The restriction function is designed-into the apparatus in order to cooperate with the selective fluid viscosity control function so as to amplify or exaggerate the flow-inhibition which is inherent in the characteristics of the fluid at that end of its flow range.
In the illustrated embodiments the mechanism is constructed in the form of a constant mesh gear pair mechanism having an aggregate tooth sum differential between the internal/external teeth of the gear pair, thereby producing resultant inner gear bodily movement with consequential fluid displacement via a restricted path.
In another illustrated embodiment the general arrangement is similar to that just described but with axially instead of radially facing gear surfaces.
A particularly preferred embodiment of the invention provides a method and apparatus employing a magneto-rheological fluid which is caused to change between its available physical states by actuation of permanent magnet means, thereby obviating the requirement for relatively high-voltage means for effecting this status change in an electro-rheological fluid.
In this preferred embodiment the means adopted for effecting the required structural or mechanical locking is provided by a known mechanical locking mechanism, for example of the kind employed meshing outer (ring type) and inner (pinion type) gears which provide a well known locking function which is widely used in seat adjustment mechanisms. Such mechanical locking means may, for example, be used to lock the pivotal position of a seat back. Such mechanism may also be included within the adjustment means which incorporate such gear drives or similar and which are provided to adjust the fore and aft position of the seat, to adjust the seat height, or provide other adjustments. In these cases the gear mechanism is effectively and selectively locked in position.
In accordance with this embodiment of the present invention this meshing mechanism is caused to be supplied into the nip between its meshing gears, with a medium in the form of the magneto-rheological fluid in its non-flowable physical form whereby that medium is effectively gripped and fed between the in-running teeth of that mechanism, thereby causing a jamming effect which can be compared with the effective seizure of a drive mechanism such as a piston engine, when (for example for lack of lubrication) free relative movement of its parts can no longer take place. The gear mechanism is effectively jammed by a sector-shaped element of solid material (effectively formed in-situ when the status of the magneto-rheological fluid is changed in response to user actuation of a magnetic field directed at the fluid), and is thereby rendered immovable.
It will be understood that the mechanism is in any case steplessly lockable in a chosen position by virtue of the gear design itself so that it might be thought that such provision amounts to an unnecessary duplication. In fact, in the embodiments, the two effects are supplemental or additive rather than the one being a duplication of the other as will be explained. In addition the fluid nature (in an inactivated state) of the MR/ER fluids means that the fluid can fill an occupy and clearances that may exist or develop between the mating locking mechanical components. Consequently the fluid within these clearances, when activated can solidly and rigidly take up any clearance and therefore reduce movement between the mating mechanical components of the mechanism thereby reducing backlash.
The provision of a well known and well-proved mechanical locking mechanisms for seat adjustment purposes meets the obvious requirement for compliance with regulations applying to automotive vehicles in terms of meeting repetitive application of defined loads etc etc. The addition to such a mechanism effectively causing it to selectively seize (by means of the magneto-rheological fluid) has the unexpected benefit of allowing that mechanism to be constructed at tolerance levels which enable production to be adopted on a far more economical basis than hitherto. In short, the magneto-rheological jamming or seizure mechanism enables a cheap mechanical seat lock to perform as if it were manufactured to the highest (or anyway at least higher than those actually adopted) manufacturing standards in terms of tolerances etc.
Thus, this aspect of the invention provides a mechanical seat portion adjustment mechanism comprising a mechanical adjustment mechanism comprising a pair of in-running meshing gears, or other drive devices, in which provision is made for jamming or seizure by the use of a rheological fluid and corresponding status-adjustment means therefor, whereby lesser standards of manufacturing precision can be adopted while providing a satisfactory level of absence of mechanical backlash, lost motion or the like.
Constructional details of a suitable mechanical seat adjustment mechanism involving in-running gears are to be found, for example, in UK Patent applications GB 2,311,094 and GB 2,073,311 which are incorporated herein by reference. These prior patents describe such mechanisms generally. It should be noted that as described in these prior patents a certain degree of clearance and tolerance in the meshing of the teeth is required in these type of locking drive mechanisms. This is due in particular to the differential in the number of teeth of each of the gears and their specific arrangement which provides the locking function. However such a clearance and tolerance in the meshing of the gear teeth does introduce backlash into the mechanism which is generally undesirable. Accordingly these propr patents describes specific mechanical modifications to such mechanism aimed to address the above described problem of backlash and play in such mechanisms. Other patents for such similar arrangements and other proposals to which the invention is also applicable and beneficial also exist.